In recent years the historically minor expenses attributable to utilization of the mails have significantly increased as a result of both direct and indirect mailing costs. As these expenses continue to spiral upwardly, the mailing habits of major industries are coming under closer scrutiny with a view to controlling such expenses. In this connection, many major manufacturers of postage meters and systems, including the assignee of the present invention, have recently introduced lines of meterscale systems, which basically include a highly sensitive scale coupled to a postage meter which automatically prints the proper postage for franking the mailpieces weighed on the scale.
Other successful means have been devised for reducing indirect mailing costs. For example, the assignee of the present invention recently introduced a system for remotely resetting postage meters to eliminate the labor costs which would otherwise be incurred for hand-carrying postage meters to the local Post Office for resetting purposes.
With the above thoughts in mind, it should be appreciated that there is a need in the marketplace to provide suitable means for making a record of direct mailing costs on a current basis for cost analysis and other mail control purposes. In a typical office or corporate mailing room, a number of users have access to a single mailing machine and the postage meter associated therewith. In these situations, it is often desirable to account for the postage used by each person or department within the office. An automated system for providing this function is described in co-pending U.S. patent application, Ser. No. 108,061, filed Dec. 28, 1979, and assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference.
In the apparatus of the above identified application, an encoder is shown for use with a postage meter. The encoder has a lever which is movable among a plurality of postage value selecting positions. The encoder includes framework adapted for removably mounting the encoder in operating relationship with respect to the postage meter, and includes means for monitoring movement of the postage meter setting lever on the meter when the encoder is mounted in the operating relationship. The monitoring means includes means for providing an electrical signal which varies in response to movement of the postage meter setting lever from one of the positions to another of the positions.
The encoder includes transducer assemblies which include a conventional variable linear potentiometer with a stationary linear resistance. As a postage meter setting lever is moved from one position to another, the resistance of the potentiometer varies, thus varying the value of the electrical signal.
The electrical signal generated by the potentiometer is converted by an analog to digital converter to a digital value. This value, as well as other data input by means of a keyboard to the accounting system, is stored in a volatile memory within the accounting system.
As with all electronic data processing systems using volatile memories, an interruption or irregularity in the power supply maintaining data in the volatile memory can cause the loss of data therein. Of course, this unfortunate phenomenon has been generally recognized ever since volatile memories have been used in data processing devices. Many attempts have been made to reduce or eliminate the possibility of loss of data during an interruption of power to the memory.
U.S. Pat. No. 4,145,761, issued to Gunter et al, discloses a volatile random access memory internal to a microprocessor powered by a stand-by voltage supply. The memory is used as a scratch pad. The voltage supply maintains data in the memory during power up and power down conditions. It is clear that the data will be maintained in the memory only as long as the stand-by voltage supply continues to supply power. Moreover, the data remains in the memory and is humanly unreadable in that form.
U.S. Pat. No. 3,859,638, issued to Hume, Jr., teaches the use of a stand-by power supply actuated upon main power supply failure. This system, similar to the invention disclosed above, has all of the limitations previously described.
U.S. Pat. No. 4,085,311, issued to Ohsako et al, discloses an integrated circuit counter and an auxiliary power source to maintain the data in the counter despite interruption of the main power supply. As in the previous systems, the data is maintained in this volatile memory during power down conditions. The limitations of dependency on an independent backup battery and human unreadability inherent in the inventions described above are likewise inherent in this invention.
U.S. Pat. No. 3,980,935, issued to Worst, discloses an elaborate power supply system comprising a main power supply, a secondary power supply, a power switch, and a battery back-up supply. The purpose of these power supplies is to maintain voltages to a volatile memory during termination of AC supply. The secondary power supply is used to sense failure of the main power supply to provide time for the backup battery to be connected to the volatile memory. Even with the additional complication of power supplies, however, the data is maintained in the volatile memory and the limitations of this invention are identical to the limitations decribed above.
Finally, U.S. Pat. No. 4,224,506, issued to Coppola et al., describes apparatus for preserving data that had been stored in a volatile memory during power down conditons. In this system, when a power interruption is detected, the system transfers data from the volatile memory to a non-volatile memory. Consequently, a loss of power does not adversely affect the integrity of the data originally stored in the volatile memory. The invention described in the above reference requires the use of an additional memory (i.e., a non-volatile memory). Moreover, the data transferred from the volatile memory to the non-volatile memory is not humanly readable.